USB Sleep

Let drives behind USB-SATA bridges spin down on Unraid.

Latest release Supported Unraid versions License: MIT

An Unraid plugin that lets drives behind USB-SATA bridges spin down.

The problem

Unraid spins drives down through /usr/local/sbin/sdspin, which calls hdparm -y and hdparm -C. Many USB-SATA bridges (for example the WD Elements Desktop, USB ID 1058:25a3) carry out these commands correctly but answer with SCSI sense data 00/1d, "ATA pass-through information available". hdparm then prints:

SG_IO: bad/missing sense data, sb[]:  f0 00 01 00 50 00 00 0a 00 00 00 00 00 1d ...

sdspin treats that message as a failure, so the syslog shows:

emhttpd: sdspin /dev/sda down: 1

After that failure, emhttpd stops trying to spin the drive down. It also keeps polling SMART attributes every poll_attributes seconds, because it believes the drive is still spinning. Those polls wake the drive if anything else puts it to sleep.

What the plugin does

The plugin keeps Unraid's script as /usr/local/sbin/sdspin.orig and installs a small wrapper in its place. The wrapper runs the original first. Only when the original reports an error (exit code 1) does it check the actual power state with smartctl -n standby, which reads it correctly through these bridges without waking the drive. Exit codes stay the same as sdspin's, so emhttpd and Unassigned Devices behave as they do for internal SATA drives.

Drives that already work are not affected: any result other than 1 from the original script is passed through unchanged.

Installation

In the Unraid web UI, open Plugins → Install Plugin and paste:

https://raw.githubusercontent.com/andrebrait/unraid-usb-sleep/main/usb-sleep.plg

If emhttpd has already logged sdspin /dev/sdX down: 1 for a drive, it will not retry until it detects the drive again. Reboot, or unmount and re-plug the drive.

Removing the plugin restores Unraid's original sdspin.

Checking that it works

sdspin sdX down; echo $?     # 0
sdspin sdX status; echo $?   # 2 while spun down

Other things that keep drives awake

The plugin only fixes the spin-down command. Periodic access will still wake the drive. One common example is the ZFS Master plugin's refresh interval, which writes to the pool history of every ZFS pool every 30 seconds while a web UI tab is open.

Testing

./test.sh runs the wrapper embedded in usb-sleep.plg against stubbed sdspin.orig and smartctl and checks each exit code.